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@ -1,18 +1,16 @@
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#![allow(dead_code)]
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extern crate rand;
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// An ordered collection of `T`s.
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enum BinaryTree<T> {
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Empty,
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NonEmpty(Box<TreeNode<T>>)
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NonEmpty(Box<TreeNode<T>>),
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}
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// A part of a BinaryTree.
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struct TreeNode<T> {
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element: T,
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left: BinaryTree<T>,
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right: BinaryTree<T>
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right: BinaryTree<T>,
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}
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#[test]
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@ -26,37 +24,42 @@ fn binary_tree_size() {
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}
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#[test]
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fn test_hand_building_tree_of_planets() {
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fn build_binary_tree() {
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use self::BinaryTree::*;
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let jupiter_tree = NonEmpty(Box::new(TreeNode {
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element: "Jupiter",
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left: Empty,
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right: Empty
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right: Empty,
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}));
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let mercury_tree = NonEmpty(Box::new(TreeNode {
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element: "Mercury",
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left: Empty,
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right: Empty
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right: Empty,
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}));
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let mars_tree = NonEmpty(Box::new(TreeNode {
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element: "Mars",
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left: jupiter_tree,
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right: mercury_tree
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right: mercury_tree,
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}));
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let venus_tree = NonEmpty(Box::new(TreeNode {
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element: "Venus",
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left: Empty,
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right: Empty
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right: Empty,
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}));
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let uranus_tree = NonEmpty(Box::new(TreeNode {
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element: "Uranus",
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left: Empty,
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right: venus_tree
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right: venus_tree,
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}));
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let tree = NonEmpty(Box::new(TreeNode {
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element: "Saturn",
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left: mars_tree,
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right: uranus_tree
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right: uranus_tree,
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}));
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assert_eq!(tree.walk(),
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@ -80,18 +83,20 @@ impl<T: Clone> BinaryTree<T> {
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impl<T: Ord> BinaryTree<T> {
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fn add(&mut self, value: T) {
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match *self {
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BinaryTree::Empty =>
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BinaryTree::Empty => {
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*self = BinaryTree::NonEmpty(Box::new(TreeNode {
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element: value,
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left: BinaryTree::Empty,
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right: BinaryTree::Empty
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})),
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BinaryTree::NonEmpty(ref mut node) =>
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right: BinaryTree::Empty,
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}))
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}
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BinaryTree::NonEmpty(ref mut node) => {
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if value <= node.element {
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node.left.add(value);
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} else {
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node.right.add(value);
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}
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}
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}
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}
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}
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@ -113,18 +118,22 @@ fn test_add_method_2() {
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let mut tree = BinaryTree::Empty;
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tree.add("Mercury");
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tree.add("Venus");
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for planet in vec!["Mars", "Jupiter", "Saturn", "Uranus"] {
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for planet in vec!["Mars", "Jupiter", "Saturn", "Uranus"] {
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tree.add(planet);
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}
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assert_eq!(tree.walk(),
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vec!["Jupiter", "Mars", "Mercury", "Saturn", "Uranus", "Venus"]);
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assert_eq!(
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tree.walk(),
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vec!["Jupiter", "Mars", "Mercury", "Saturn", "Uranus", "Venus"]
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);
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}
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// From chapter 15: Iterators
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use self::BinaryTree::*;
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// The state of an in-order traversal of a `BinaryTree`.
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struct TreeIter<'a, T: 'a> {
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struct TreeIter<'a, T> {
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// A stack of references to tree nodes. Since we use `Vec`'s
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// `push` and `pop` methods, the top of the stack is the end of the
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// vector.
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@ -164,14 +173,13 @@ impl<'a, T> Iterator for TreeIter<'a, T> {
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type Item = &'a T;
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fn next(&mut self) -> Option<&'a T> {
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// Find the node this iteration must produce,
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// or finish the iteration.
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let node = match self.unvisited.pop() {
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None => return None,
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Some(n) => n
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};
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// The next node after this one is the leftmost child of
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// this node's right child, so push the path from here down.
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// or finish the iteration. (Use the `?` operator
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// to return immediately if it's `None`.)
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let node = self.unvisited.pop()?;
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// After `node`, the next thing we produce must be the leftmost
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// child in `node`'s right subtree, so push the path from here
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// down. Our helper method turns out to be just what we need.
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self.push_left_edge(&node.right);
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// Produce a reference to this node's value.
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@ -188,24 +196,40 @@ fn external_iterator() {
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}
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// Build a small tree.
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let subtree_l = make_node(Empty, "mecha", Empty);
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let subtree_rl = make_node(Empty, "droid", Empty);
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let subtree_r = make_node(subtree_rl, "robot", Empty);
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let tree = make_node(subtree_l, "Jaeger", subtree_r);
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let mut tree = BinaryTree::Empty;
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tree.add("jaeger");
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tree.add("robot");
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tree.add("droid");
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tree.add("mecha");
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// Iterate over it.
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let mut v = Vec::new();
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for kind in &tree {
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v.push(*kind);
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}
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assert_eq!(v, ["mecha", "Jaeger", "droid", "robot"]);
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assert_eq!(v, ["droid", "jaeger", "mecha", "robot"]);
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assert_eq!(tree.iter()
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.map(|name| format!("mega-{}", name))
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.collect::<Vec<_>>(),
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vec!["mega-droid", "mega-jaeger",
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"mega-mecha", "mega-robot"]);
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let mut iterator = (&tree).into_iter();
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assert_eq!(iterator.next(), Some(&"droid"));
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assert_eq!(iterator.next(), Some(&"jaeger"));
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assert_eq!(iterator.next(), Some(&"mecha"));
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assert_eq!(iterator.next(), Some(&"robot"));
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assert_eq!(iterator.next(), None);
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// Construct a tree by hand.
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let left_subtree = make_node(Empty, "mecha", Empty);
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let right_subtree = make_node(make_node(Empty, "droid", Empty),
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"robot",
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Empty);
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let tree = make_node(left_subtree, "Jaeger", right_subtree);
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// Try initializing the iterator ourselves and see if it runs.
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let mut v = Vec::new();
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let mut iter = TreeIter { unvisited: vec![] };
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iter.push_left_edge(&tree);
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@ -214,33 +238,23 @@ fn external_iterator() {
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}
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assert_eq!(v, ["mecha", "Jaeger", "droid", "robot"]);
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// Iterate by shared reference.
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let mut v = Vec::new();
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for kind in &tree {
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v.push(*kind);
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}
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assert_eq!(v, ["mecha", "Jaeger", "droid", "robot"]);
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// Iterate, taking ownership.
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let mut v = Vec::new();
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let mut state = tree.into_iter();
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while let Some(kind) = state.next() {
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v.push(*kind);
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}
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assert_eq!(v, ["mecha", "Jaeger", "droid", "robot"]);
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assert_eq!(tree.iter()
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.map(|name| format!("mega-{}", name))
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.collect::<Vec<_>>(),
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vec!["mega-mecha", "mega-Jaeger",
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"mega-droid", "mega-robot"]);
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let mut iterator = tree.into_iter();
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assert_eq!(iterator.next(), Some(&"mecha"));
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assert_eq!(iterator.next(), Some(&"Jaeger"));
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assert_eq!(iterator.next(), Some(&"droid"));
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assert_eq!(iterator.next(), Some(&"robot"));
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assert_eq!(iterator.next(), None);
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}
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#[test]
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fn other_cloned() {
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use std::collections::BTreeSet;
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@ -257,13 +271,12 @@ fn other_cloned() {
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#[test]
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fn fuzz() {
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fn make_random_tree(p: f32) -> BinaryTree<i32> {
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use rand::{ThreadRng, thread_rng};
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use rand::distributions::range::Range;
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use rand::distributions::Sample;
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use rand::prelude::*;
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use rand::thread_rng;
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use rand::rngs::ThreadRng;
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fn make(p: f32, next: &mut i32, rng: &mut ThreadRng) -> BinaryTree<i32> {
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let mut range = Range::new(0.0, 1.0);
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if range.sample(rng) > p {
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if rng.gen_range(0.0 .. 1.0) > p {
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Empty
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} else {
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let left = make(p * p, next, rng);
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Jim Blandy
3 years ago